The present invention relates to method and apparatus for electrically connecting an explosion-proof electric motor to an electric power cable. More specifically, the present invention relates to a sealed housing for storing the electrical connection between the motor and the electric power cable.
Electrically operated equipment that is intended for use in coal mines and similar controlled environments must conform to strict construction and design requirements to insure safety for its intended use. Among the requirements are those intended to prevent an electrical motor from causing an explosion in a mine environment. These types of motors are referred to as xe2x80x9cexplosion-proof motors.xe2x80x9d The Code of Federal Regulations provides detailed specifications for explosion-proof motors for use in coal mines and similar controlled environments, such as the requirements for the openings in the motor enclosure to be sealed. An electrical spark within an electric motor could ignite coal dust, grain dust, or any other airborne volatile substance, producing an explosion. Therefore, the requirements regarding the openings in the motor enclosure are an important preventative measure to keep such explosive substances out of the motor and any sparks generated by the motor in the motor housing.
Electric motors must be supplied with electrical power to operate. Typically, a power cable is routed to the electric motor through a sealable opening in an explosion-proof motor housing. An access panel is typically provided so that a cable installer can enter the interior of the explosion-proof motor housing to access the power cable and motor conductors in order to electrically connect them together. The access panel also has to conform to the requirements for openings in an explosion-proof motor housing. Once the connection is made, the power cable and motor conductors are forced back into the explosion-proof motor housing. The access panel is then secured to the motor housing.
Forcing the motor conductors and power cable back into the explosion-proof motor can result in damage to the motor leads, as well at to the power cable. The motor conductors and power cable may experience abrasion when forced through a constriction. Additionally, rotating portions of the electric motor may damage the motor conductors and power cable if these extend too far into the housing. Thus, a need exists for an explosion-proof motor, and for a method of electrically connecting an explosion-proof to power, that can protect the motor conductors and power cable from damage.
The present technique features an explosion-proof motor designed to respond to such needs. The explosion-proof motor assembly comprises an electric motor and an explosion-proof motor housing. The electric motor has a plurality of motor conductors. The explosion-proof motor housing comprises a first opening for receiving a power cable, a second opening for routing a power cable and the plurality of motor conductors to an exterior location. The explosion-proof motor housing also has a connection housing that is securable to the explosion-proof motor housing to seal the second opening. The connection housing has an internal volume to house the power cable, the plurality of motor conductors, and an electrical connection formed between the power cable and the plurality of motor conductors.
According to another aspect of the present technique invention, a connection housing for an explosion-proof electric motor is featured. The explosion-proof electric motor has a housing with a central volume to house an electric motor. The electric motor has motor conductors extending from the central volume through a passageway to the connection housing. The connection housing comprises a removable enclosure. The removable enclosure has an internal volume to house an electrical connection formed between the power cable and the motor conductors. Additionally, the removable enclosure houses substantially all excess length of the power cable and motor conductors.
The technique also features a method of wiring a power cable to an explosion-proof motor. The method comprises the act of disposing a plurality of power conductors through an opening in the explosion-proof motor housing to an exterior location. A plurality of stator conductors are routed through the opening in the explosion-proof motor housing. Electrical connections are formed between the plurality of power conductors and the plurality of stator conductors. The electrical connections and substantially all excess length of the power conductors and motor conductors are housed in a connection housing sealingly secured to the motor housing.
According to another aspect of the present technique, an explosion-proof motor comprises a stator having a stator conductor electrically coupled to a stator winding, and an explosion-proof motor housing. The explosion-proof motor housing has a first housing for housing the stator. The motor housing also has an end bracket securable to the rotor and stator housing. The end bracket has a first opening for receiving a power cable, and a second opening for routing a motor conductor and a third opening for routing the power cable and motor conductor. The explosion-proof motor housing also has a second housing securable to the end bracket to seal the second opening. The second housing has an internal volume to house an electrical connection formed between the power conductor and stator conductor, and excess portions of the power conductor and motor conductor. The internal volume is such that no excess portions of the power conductor and motor conductor need be disposed through the second opening when the second housing is secured to the first housing.